Component of the zona pellucida, an extracellular matrix surrounding oocytes which mediates sperm binding, induction of the acrosome reaction and prevents post-fertilization polyspermy. The zona pellucida is composed of 3 to 4 glycoproteins, ZP1, ZP2, ZP3, and ZP4. ZP1 ensures the structural integrity of the zona pellucida. This is the function of ZP1 (zona pellucida glycoprotein 1, Ensembl gene identifier ENSG00000149506).